1. Field of the Invention
The present invention relates to flat virtual displays and, more particularly, to a virtual display comprising a thin display, such as a liquid crystal display (LCD), a microlens array, and an aperture array. The aperture array is configured to direct pin-points of light from the display onto a microlens in the microlens array. Each microlens directs a single ray of light so that the rays form a coherent image on a viewer's retina. This arrangement provides a very small, lightweight virtual display. The inventive display may be used for a head-mounted display, a display which may be embedded into a smart card, or other uses where a small, lightweight display may be advantageous.
2. Discussion of Related Art
Researchers in communications technologies continue to seek ways to provide a person with a greater sense of "being there" via networked communications. Two well known examples of providing this sense are (1) teleconferencing--which provides face-to-face communications to persons at remote locations--and (2) virtual reality--which provides a person with the feeling of actually being at a particular (real or imaginary) location.
The assignee of the present invention, Bell Communications Research Corp. (Bellcore) has developed several such new technologies. One technology developed by Bellcore is an Electronic Panning Camera (described in U.S. Pat. Nos. 5,187,571 and 5,537,737) which provides users with individually controllable views of remote locations, each view being delivered from a single non-moving camera. The Electronic Panning Camera is an inventive device and method for producing a widely pannable video signal from a composite camera with no moving parts. A composite camera is composed of several miniature standard video cameras whose fields-of-view are optically and seamlessly merged to form a broad panoramic field-of-view.
The inventor believes, however, the ultimate in visual immersion is achieved by combining the Electronic Panning Camera's ability to allow several persons to individually control their views of remote sites with techniques borrowed from the emerging field of Virtual Reality. One problem, however, with this combination, and with conventional networked virtual reality systems, is the head-mounted displays typically worn to access this experience are heavy (often weighing several pounds, with much of this weight centered forward of the user's face), uncomfortable, and often quite expensive.
Almost all attempts at virtual reality displays have used a planar display of some kind (usually a flat-panel liquid crystal display) and a lens system. FIG. 1 illustrates such a system 100. A housing 102 contains at one end a liquid crystal display (LCD) 104 and at the other end is an aperture 106 through which a user's eye 108 may look at the LCD 104. Interposed between the aperture 106 and the LCD 104 is bulk optics 110 for focusing the LCD 104 display onto the eye. Note that in order for the image on the LCD display to properly focus on the user's eye 108, there is a first length 112, which is substantially a first focal length between the LCD 104 and the optics 110, and a second length 114, which is substantially a second focal length between the optics 110 and the aperture 106. There are many variations on this structure, but each attempts to portray a highly magnified image for each of the user's eyes that appears to be placed at, or near, virtual infinity so that the eye can easily focus on it.
The resulting head-mounted displays are physically large due to (1) thick, low f-number, display-sized lenses and (2) the long optical path lengths required for these lenses. The displays are also heavy, due to the weight of the glass or plastic comprising the optics, and uncomfortable to wear because this large and heavy display/lens-system is cantilevered out over the front of the head and tends to tilt the wearer's head forward.
In more advanced head-mounted displays (e.g., those used in military aircraft), the image is often relayed by a series of mirrors and/or intermediate lenses, or even coherent bundles of optical fiber, from a display that is remote from the eye. In these cases, one or more bulk lenses (or mirrors) are again used at the end of the optical relay system closest to the user's eye to create an image that appears to be at virtual infinity. Some displays use a semi-transparent visor as part of the virtual imaging system and causes the ultimate virtual image to be displayed by way of partial refection. Again, focal lengths on the order of several inches and large reflecting surfaces make these systems cumbersome and bulky.
Refection Technology Inc. located in Waltham, Mass. provides a head-mounted display under the trade name "Private Eye". This HMD display uses a linear array of LEDs to create the image. The image of the LEDs is swept through a fixed angle by a vibrating mirror. The swept image is viewed through one or more bulk optics lenses. (This technology is used, for example, in Sega's "Virtual Boy"). Although the technique does not use a planar screen, it uses bulk optics and results in a display that protrudes from the face much more than an ordinary pair of spectacles.
A head-mounted display developed at the University of Washington at Seattle, uses a laser beam to scan directly into the eye and "paints" an image on the retina. This technique could lead to a less bulky display, but requires a rather sophisticated scanning system and multi-colored lasers for a color image. This device is difficult and expensive to implement.
Therefore, it is an object of the present invention to provide a head-mounted display for virtual reality that is light and comfortable.
It is another object of the present invention to provide a virtual display that is inexpensive to manufacture.